Okay chances are that you will ruin the blade's edge. Specially if this is your first time.
If you were to be doing this on the brand new sword, I would not recommend it. Chances are you will get it duller not sharper.
What I recommend you do is at least read a little online about the proper way of cutting with a sword. I saw your video, and will try to help you with cutting. I am not trained nor am I qualified to teach or say much about sword cutting but I committed many mistakes as you did when starting out.
Tip 1: get a bigger stand. Not it is not because it is dangerous to cut at such a low level (well it is dangerous but that's not why). The reason why is because when you crouch down to such a low level, your point of balance in your body is thrown off balance. Therefore the method of standing you have been used to for your whole life is not there anymore. You must stand at an awkward position when standing, this impacts your arms reach/agility..
This leads to tip 2:
Katana's are slicing (slashing) weapons not chopping. Swinging like a bat will cut but will not cut very well.
When you crouch down, it becomes difficult to create a true katana slash as most of us are NOT used to having such an awkward point of balance. So then how does one slash a bit better? It all starts with how you hold a katana. I will come back on this.
Tip 3
To hold a katana properly, please take your right hand and place it with your wrist
aligned with the tsuka. Keep a slightly angled hold, so that your finger before the thumb BARELY touches the tsuba. I mean BARELY, the tsuba should NOT receive any pressure. Your thumb then goes on top of your index finger.
Your left hand, and place it about 2-3 fingers length from your right hand's pinky, to your left hands next to last finger (the one before the thumb). Remember keep your wrist ALIGNED with the tsuka. Place your left hand's thumb on top of your index finger.
This is how you hold the katana.
Read here. These are stances but keep a close eye on his holding. Of course your hands will be 2-3 fingers length away from each other as his tsuka appears to be slightly bigger..
Tip 2: To slash properly one must realize the katana is a slicing weapon. Slicing in the sense of how you use a kitchen knife. You press/slide it down or up to cut.
Obviously you can't do the same with a katana for shear speed and length reasons, however what Japanese people discovered is that when you hold a katana properly, you take one short step forward, and you stretch your arms out as much as possible and swing you create a natural circle, thus giving you a slicing motion.
There is a catch... however:
The pressure exerted on the handle is divided by the fingers:
Pinky exerts most of the pressure, the more you go up on the finger count on the tsuka the less force you exert. This goes for both hands, right and left.
Try bettering your technique, if even with better technique you cannot cut the water bottle, then go on to the sharpening. If possible get in a dojo and get properly trained..